(1) Field of the Invention
This invention relates in general to linear magnetic tape recording apparatus and in particular to precision apparatus for guidedly transporting tape within such apparatus. (A "linear" tape recording apparatus, as opposed to transverse and helical scan rotary recorders, records in the direction of the longitudinal axis of recording tape. By contrast, transverse scan and helical scan recorders record in comparatively short tracks across the tape.)
(2) Description Relative to the Prior Art
In a linear magnetic recording apparatus of the type known as the SP 2000 Motion Analysis System, available from Spin Physics, Inc., San Diego, Calif., the state of the art with respect to the transportation of magnetic recording tape within such system is tested to its limits. Such a system, as has been published, must be capable of transporting tape at varying record speeds as high as 200 inches per second (ips), and as low as 6 ips--doing so while recording in 32 separate information recording tracks which are tightly packed across tape of only one-half inch width. To assure that each of the 32 information recording tracks is always reproducible during playback, it is, of course, essential that precision be built into the recording operation, i.e. by well-defining the tape path implemented within the recording apparatus.
There is, as is known, a trend toward the use of cassettes for containing magnetic tape supply and take-up reels. Such usage obviates the need for having to thread up a transport mechanism, as is required in so-caled reel-to-reel transports, e.g. the transport employed in the Honeywell 7600 Recorder, available from Honeywell Inc., Minneapolis, Minn. The use of a cassette as part of the tape-path defining apparatus is, however, a feature that is not without detraction. For example, while a cassette-type format provides easy handleability from a user standpoint, precision must be built into the cassette and into the cassette-to-recorder interface in order to have playback repeatability. By contrast, a recorder with a reel-to-reel tape path configuration employs precision components within the recorder itself, utilizing therein precision tape-tensioning and capstan-feeding of tape to assure the requisite playback repeatability.
The trade-off between a cassette-load type apparatus and a reel-to-reel transport configuration is one to economic significance: Since there will ordinarily be a greater number of recordings than there are recorders, the matter of customer convenience must significantly outweigh the desirability of building precision into the recorder apparatus itself.
In transporting magnetic tape within a linear recorder apparatus, three general tape-driving techniques are known: (1) capstanless transportation of tape by driving tape supply and take-up reels (U.S. Pat. No. 4,256,996), (2) capstan-driving tape by utilizing a cooperating pinch-roller (U.S. Pat. No. 3,801,043), the tape to be transported being squeezed between the capstan and the pinch roller and (3) capstan-driving tape (without a pinch roller) by providing a certain amount of tape-wrap about the capstan. Whereas reel-driving take-up and supply reels is generally a rather coarse tape feeding practice, the use of a capstan-and-pitch roller tape driving format is fraught with other (potential) problems: the pitch roller, aside from being an extra precision part, may cause signal-influencing magnetostriction within the tape that it "pinches"; and, when the tape is transported at high speed, there could be a transportation jam-up at the "pinch" between the capstan and pinch roller.
Whether of the type that cooperates with a pinch roller, or of the type employing tape-wrap, all known prior art linear tape recorder capstans are of a non-positionable type, the reasons for this being that the capstan is perhaps the most critical of all tape guiding parts in any linear recorder; to fix the position of a capstan, therefore, eliminates the most ready source of tape transportation problems.
With the above as background, consideration should be given to the following problem which is solved by means of the invention: